Study says medical urethanes may suffer hydrolysis

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WASHINGTON (Dec. 10, 11:15 a.m. ET) — Researchers have discovered what they call a “previously unrecognized” way that degradation can occur in silicone-urethane plastics, often used in medical devices.

The study, published in the American Chemistry Society’s journal Macromolecules, could have implications for device manufacturers considering use of these plastics in the design of some implantable devices, including cardiac defibrillation leads, ACS said in a Dec. 5 statement.

The researchers said that some implanted biomedical devices, such as pacemakers and defibrillators, have parts made of a plastic consisting of polyurethane and silicone. While these materials have been extensively studied for failure due to interaction with oxygen, no published study has looked at interaction with water as a potential failure mechanism in this class of materials, ACS reported.

In a cardiac lead application, these materials may be used as a coating on the electrical wires that carry electric current from the battery in the device to the heart. Surgeons implant pacemakers in 600,000 people worldwide and defibrillators in 100,000 people in the United States each year, ACS said. Since these implants must function reliably for years, the scientists wanted to determine whether the plastic material was suitable for long-term implants.

ACS reported that laboratory tests, including accelerated ageing of the materials under conditions that simulated the inside of the human body, found indications that the material begins to break down within 3-6 years.

“By making the conclusions of this novel, scientific research public in a respected peer-reviewed journal, device manufacturers may now consider these important findings in their device designs,” commented Kimberley Chaffin, lead author of the report.

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